1. Field of the Invention
This invention relates to a short code subscription apparatus for a telecommunications network, and to a method of making calls through the network using short codes.
2. Related Art
In conventional telecommunication networks, calls are usually connected on the basis of a diallable number which forms part of a defined numbering plan. Conventional telephone numbers typically comprise a large number of digits, typically nine or more, although in certain circumstances they may comprise as few as five or six digits for local calls on the fixed PSTN (public switched telephone network). Alternatively, short codes of for example two or three digits can be used in private networks. These short codes can be used with a look-up memory in order to access a full telephone number on the basis of a short code. The term "short code" is used in this specification to mean a code which is shorter than the normal telephone number of the line accessed by the code. Because such codes are short they are easy to find fortuitously, making access control difficult.
It is possible to configure a service that allows a mobile user to access a data converting device, commonly known as a Packet Assembler/Diassembler (PAD), so that communications with database hosts and other users on a Packet Switched Public Data Network (PSPDN) can be made. Existing systems within the GSM (Global System for Mobile communication) standard can be used to identify short codes of the kind described above to allow access to a PAD, but there is no management of authorisation of access to a specific PAD by the GSM network so, in order to provide security, the user of the mobile station needs to enter a specific password and comply with other security measures in order to gain access into the private network after the initial connection has been established to the private network by the use of the short code, thereby preventing accidental or deliberate use of the short code to gain unauthorised access. These additional security measures need to be performed after the call has been connected, and so if the user is not permitted access, network resources have been wastefully used up during the failed connection process. Furthermore, the use of passwords is inconvenient for the mobile user, and defeats the advantages of short code access.
Services such as call screening can be used to provide a measure of security for the dialled station, by determining the number of the dialling station. This service is provided for the security of the dialled station, so the recipient of the call may be required to pay for this benefit. Also, since the screening takes place at the dialled station, network resources are used to make the initial connection, which is wasteful if the call is to be rejected.